It is extremely inconvenient to mount and dismount existing wall lamps, particularly a street lamp, an industrial mining lamp, a stage lamp, etc. A common wall lamp is provided with a power adapter. To protect the power adapter, a wall lamp is usually installed in a closed space, and mostly installed within the lampshade. Therefore, it is very inconvenient to mount, and dismount the wall lamp. After the wall lamp is fixed to the wall, a power supply needs to be connected to the wall lamp. The old installation method suggests to connect a power supply first and then the lamp is fixed on the wall. This method of installation is extremely inconvenient. The wall lamp may easily slip during the installation process. This slippage may cause damages. Further, the connected power line may fall off as a result of slippage of the lamp body. The fall of the power line may lead to a potential safety hazard. Moreover, in an existing wall lamp, the illumination direction of the lamplight cannot be adjusted arbitrarily after installation. This is an undesirable effect of the current method of installation. Therefore, there is a need for a wall lamp, which can easily be mounted and dismounted and can be easily adjusted in terms of the light path direction.